Builder: Kure Navy Yard.
Laid Down: 4 November 1937.
Launched: 8 August 1940.
Commissioned: 16 December 1941.
Fate: Blew up and sank on 7 April 1945 at 1435 hours south west of Kyuscho while on a suicide run to Okinawa after being hit by 11-13 torpedoes and at least 7 bombs.
Builder: Nagasaki Yard, Mitsubishi Co.
Laid Down: 29 March 1938.
Launched: 1 November 1940.
Commissioned: 5 August 1942.
Fate: Lost headway and sank on 24 October 1944 in the Sibuyan Sea, south of Luzon after sustaining 20 torpedo hits and 17 bombs.
Particular Preparations For Construction
When the construction of the Yamato class was planned, there was no shipyard in Japan capable of building such ships without expanding it's building facilities.
Since the Japanese Navy intended to build four Yamato class ships in succession, special preparations for their construction had to be made in selected shipyards.
Some of these arrangements consisted of expanding dock capacities, building a special transport ship capable of carrying an 18 inch gun turret and hiding such a vessel behind sisal rope curtains for security reasons.
The depth of the building dock at the Kure naval yard, in which the Yamato was built, was deepened about 3 feet so that the hull could be floated in the dock.
The capacity of the gantry crane straddling the dock was increased to 100 tons in order to lift heavy armor plates. Furthermore, about a quarter of the dock at the landward end was covered with a roof to prevent it from being seen from a prominent hill nearby.
In the Yokosuka district a large dry dock was specially built and the third ship of the Yamato class, later named Shinano and converted into a carrier was built there.
The Nagasaki Yard of Mitsubishi Heavy Industries Co. Ltd. was the only other shipyard capable of building a Yamato class battleship. even with some expansion of it's facilities.
Unlike Kure's building dock a slipway was to be used for the construction there. Needless to say, the launching of a vessel weighing 30,000 tons raised various problems technically. Not only was the slipway strengthened but workshops and piers were also expanded or strengthened. The overall area of the expansion of the workshops reached a total of almost 787,401 square feet. Floating cranes of 350 tons and 150 tons were built and installed to lift heavy armor plates and gun fittings.
At Sasebo, one of the three major naval bases in Japan, a dry dock capable of accommodating a Yamato class battleship was also built.
Some measures taken to safeguard the security of the Musashi were interesting.
The slipway on which she was built was covered by a sisal rope curtain.
The total length of rope used reached 1,683 miles and it's weight totaled 408 tons. This great consumption of sisal rope caused a temporary shortage of this item on the market, and caused complaints among fishermen.
One more thing to be mentioned was the construction of a transport vessel to carry the 18 inch guns and turrets from Kure to either Nagasaki, where the Musashi was being built, or to Yokosuka, where the Shinano was to be built.
These 18 inch guns and turrets were manufactured at the Kure naval yard and they could be transported only by this specially-built vesse
Even in accommodation the Yamato had remarkable features.
She was the first Japanese warship to be equipped with an air conditioning system.
Although this comfort was not afforded to all the living quarters, the Yamato and her sister Musashi had a favorable reputation among sailors as the most comfortable ships in the Japanese Navy.
Design: 61,890 tons.
Standard: 63,200 tons.
Trial: 69,100 tons.
Full Load: 72,809 tons
Overall: 863.5' (263.2m)
Waterline: 830.0' (253m)
Beam: 127.6' (38.9m)
Draught (full load): 35.62' (10.9m)
Features Of The Hull
One of the more notable features of the Yamato's hull was that her displacement/length ratio was great, and her speed/ length ratio was small, compared with other battleships. While these ratios for the IJN Nagato was 98.14 and 1.001 respectively as compared with 101 and 0.852 for the Royal Navy's battleship Nelson, those of the new Japanese battleship were 112.2 and 0.94 respectively. Moreover her block co-efficient was 0.612, perhaps the highest figure among all the battleships in the world. This meant that she had great beam and shallow draught for such a big displacement.
Reduction of the Yamato's draught as much as possible was a prime consideration, in view of port facilities and naval bases in Japan. Nevertheless her draught when fully loaded reached 35.63 feet and some areas of the naval bases and extensive portions of the approaches to dry docks used by warships of this class had to be dredged accordingly.
How to reduce the hull resistance and increase the propulsive efficiency was the next problem which the designers strove to solve. Tests were conducted with various hull models in the experimental model basin of the Naval Technical Research Establishment in Tokyo. This basin was the largest in Japan, having a length of 805.54 feet, a width of 41 feet and a depth of 21.35 feet.
These thorough and extensive experiments led to the adoption of a gigantic bulbous bow, the size of which few other naval architects had ever planned. The result was unique; the reduction of the hull resistance by the use of this bulbous bow reached 8.2% at a speed of 27 knots.
By improving the fitting of the shaft brackets and the bilge keels, a further reduction in the hull resistance was achieved. Represented in terms of effective horsepower, the former resulted in the saving of 1,900 ehp and the latter 475 ehp. Altogether including the reduction in resistance by the use of the bulbous bow, these savings totaled 7,910 shp or 15,820 shp.
In the full power trial runs, the 69,500 ton Yamato, powered by 153,553 SHP made 27.46 knots. EHP at this time was calculated at 76,700 hp, the propulsive efficiency at her standard speed of 18 knots proved to be 58.7%. Such efficiency was obtained by only a few vessels of the Japanese Navy.
Another important feature was the extensive use of lap-joints in the midship part of the shell plating. The butt-joint had long been used in shell plating to make the shell surface smooth, thus reducing it's frictional resistance. However a serious defect had been found in the outer bottom butt-joint plates of the Isuzu class light cruisers and Fubuki class destroyers. This led to the apprehension regarding the use of butt-joints on the Yamato's shell plating. On the other hand, it was learned that frictional resistance was greatly affected by the surface of the fore and aft parts of the ship, where the water pressure was greater then amidships. Based on this finding, butt-joints were used in the fore and aft parts of the Yamato; the remaining part was covered by lap-joint plating. The method proved very effective when the ship was completed.
In the hull structure, too, several new measures were adopted to ensure the required strength and at the same time, save weight:
Here are some examples;
First some of the armor was fitted to serve as hull strength members.
The lower side armor was fitted to serve dually as longitudinal members. This was a unique method that the Japanese Navy had applied to medium armor plating since it was first applied to the Heavy cruiser Furataka, whose characteristics surprised world shipbuilding circles at the time.
Second, electric welding was employed extensively except in the longitude members. The Japanese Navy was rather early in applying welding to the construction of ship's hulls. The 10,000 ton submarine tender Taigei, which was completed in 1934, was the first ship in the Japanese Navy with a completely welded shell.
However, two subsequent disasters, which involved Japanese men of-war led to a thorough investigation of shipbuilding techniques. In March, 1934 a small destroyer capsized in heavy weather, while in September of the following year, two large destroyers broke in two and another sustained heavy damage in rough weather. An extensive and thorough investigation as then carried out. The wisdom of welding was also reviewed, and it was decided not to use welding in such important portions as longitudinal structure members.
Most of the Yamato's upper structure was constructed by means of welding. The largest welded block for the Yamato was 36 feet high and weighed 80 tons. The total length of the welded portions of the Yamato reached 1,521,601 feet and the total number of welding rods used in the construction was 7,507,536. By comparison the total number of rivets was 6,153,030.
Third,the main portion of the longitudinal structure was constructed with Ducol steel, while other portions were built of mild steel.
Fourth, the central longitudinal bulkhead was duplicated as it was to support heavy 7.87 inch thick armored deck plates, 127.62 feet at their greatest breadth. To ensure the reliability of the electric circuits, the central ringman electric circuit ran through the watertight compartment inside the central bulkhead.
Another unique feature was her flush weather deck from bow to stern, giving her an extraordinary appearance for a battleship. The idea was to make the longitudinal members continuos so as to be most effective and at the same time save structural weight. This method had been adopted in building Japanese warships ever since it first applied to the heavy cruiser Furataka.
The Yamato's stern casing , which had to support her heavy 2,490 ton stern portion was an extraordinary one too. Made of cast steel, it weighed 91.3 tons
The Yamato's turning ability was excellent.
Her tactical diameter, when turned by a maximum rudder angle of 36 degrees at a speed of 26 knots was 2099 feet.
These figures were considered superior when compared to other battleships.
The Yamato had two rudders, the main and auxiliary, instead of the twin-rudder system of ordinary large warships.
Originally it was planned to install two rudders, one each fore and aft, in view of the fact that the German Bismarck finally lost her maneuverability ability due to damage to her rudders .
But the design was later changed so as to install the auxiliary rudder about 49 feet ahead of the main one.
In her trial runs it was discovered that the auxiliary rudder alone was unable to stop the momentum of a turn once started.
Stability And Trim Under Damaged Conditions
Compared with other Japanese battleships, the Yamato was well designed to survive in a damaged condition.
This was well demonstrated in the Yamato's last hours and that of her sister Musashi, although both were eventually sunk.
The Yamato's fore freeboard was 32.8 feet and aft was 20,9 feet .
These figures were remarkable compared with the Nagatos', which was 25.9 feet and 15.7 feet respectively.
Accordingly her reserve buoyancy reached as much as 54,450 tons compared to 29,292 tons for the Nagato.
The Yamato was designed to maintain stability until her heel reached 20 degrees.
Tora! Tora! Tora!